The field of the invention is that of micro-instrumentation, that is, articulating, hand-held, instruments used in micro-surgery, electronic micro-assembly and like applications, for grasping, cutting, punching out, probing and the like. The instruments can comprise scissors-handle actuators, so-called cigar handle linear or rotary activators, or other actuators, with push or pull force application design modes.
The invention is particularly advantageous for endoscopic, or minimally invasive, surgery, but is also advantageous in other applications for micro-instrumentation.
Prior art endoscopic surgical instruments are shown in U.S. Pat. No. 5,152,780 to Honkanen et al. and U.S. Pat. No. 5,219,357 to Honkanen et al., which disclose, respectively, the use of one or two jaws rotatably mounted on one or two pivots that are integrally formed with a wall that is part of the frame of the instrument, while a linkage mechanism movable relative to that wall effects rotation of the jaw or jaws. The integral nature of the pivot or pivots provided the advantages of resulting in fewer parts to assemble and possibly accidentally disassemble inside a patient and of providing strength to the working portion of the instruments, avoiding breakage inside a patient.
A disadvantage of the integral pivot mechanisms disclosed in the prior art arises from the fact that the jaws disclosed therein are provided with a straight slot ending in a semicircular bearing surface which engages or seats an integral pivot of cylindrical or hour-glass shape. The straight slot, along which the pivot slides in assembly, also provides an unwanted degree of freedom in operation. Thus, in the disclosed mechanism, when the jaw is pulled proximally to the operator to open the jaw, the jaw may slip linearly along the slot relative to the pivot until the jaw hits a bulkhead, which, for example is explained at U.S. Pat. No. 5,152,780, col. 3, lines 25-28, as a "ramp surface" of the outer tip assembly including the pivot wall. Close tolerance with the ramp surface is difficult and therefore expensive to achieve, while a wider gap results in unwanted "play", uneven wear, and even the possibility of lodging of unwanted debris.